1. Field of the Invention
This invention relates to a projection type image display device that changes the optical path of an image from a projector using a reflecting mirror and projects a resultant image on a screen from behind, and more particularly to an image distortion correcting mechanism used to correct image distortions generated by the use of the reflecting mirror.
2. Description of the Related Art
As shown in FIG. 9, a multivision device includes a plurality of rear projection type image display devices (rear projectors) arranged in the vertical and horizontal directions, and the output images of the projectors are projected to display an image on a large screen.
In FIG. 9, a projector 1 provided in a prescribed lower position in a cabinet 7 emits an output image upwardly from its projection lens. The emitted output image has its optical path changed by a reflecting mirror 3 provided in a prescribed position in the cabinet and projected on a screen 4 provided at the front surface of the cabinet 7. A position adjuster 2 having the projector 1 thereon can adjust the position of the image to be projected on the screen 4 relative to the screen 4.
In the rear projection type image display device having the conventional reflecting mirror 3, it is difficult to accurately project an image from the projector 1 on the screen 4, and therefore the position adjuster (six-axis adjuster) is used to adjust the image in the optimum position. However, the position adjuster 2 is capable of adjusting only the position of the projector 1 in the vertical and horizontal directions, the magnifying/reducing direction, the rotation direction, and the vertical trapezoidal and horizontal trapezoidal directions, and is not capable of correcting image distortions generated by the reflecting mirror 3 and optically caused image distortions.
In order to improve the disadvantage, an adjusting mechanism that changes the flatness of the reflecting mirror 3 at its periphery depending on each necessary unit of the reflecting mirror 3 (see for example JP-A-2001-109071) is provided or the phenomenon that a projected image is distorted at the periphery (pincushion distortion) is corrected by pressing in a setscrew to press the vicinity of the center of each of the sides of the reflecting mirror 3 so that the reflecting mirror is deformed into an arch shape (see for example JP-A-2002-77777).